From 1996 to 2012, 3,928 cases of human anaplasmosis (HA) (formerly known as human granulocytic ehrlichiosis) were reported in Minnesota. In 2012, 507 confirmed or probable anaplasmosis cases (9.5 cases per 100,000 population) were reported (Figure 1). The median number of 317 cases (range, 139 to 782 cases) reported from 2004 through 2012 is also considerably higher than the median number of cases reported annually from 1996 to 2003 (median, 56 cases; range, 14 to 149).
The number of anaplasmosis cases has been increasing since the first cases of HA were reported in Minnesota in the mid-1990s. A variety of factors, including increasing physician awareness, increasing infection rates in ticks, and expanding tick distribution, may have led to this trend.
The HA cases in 2012 ranged in age from 1 to 99 years; the median age (56 years) was greater than that of Lyme disease (39 years). In 2012, 61% of HA cases were male.
- Reported Cases of Human Anaplasmosis in Minnesota by Year
Graph showing the number of reported human anaplasmosis in Minnesota by year.
- Reported Cases of Human Anaplasmosis in Minnesota by Month of Onset
Graph showing the percent of cases of human anaplasmosis by month of onset.
Most HA cases report likely exposure to blacklegged ticks in the same east-central and north-central Minnesota counties where the risk of Lyme disease is greatest.
- High Risk Areas for Tick-borne Diseases in Minnesota
A map that shows counties of highest Tick-borne risk in Minnesota.
- Anaplasmosis, 2012
Minnesota Department of Health, Disease Control Newsletter;
Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2012.